1. Field of the Invention
The present invention relates to digital video transmission systems and, more particularly, to testing digital video transmission systems.
2. Description of the Related Art
As the market and number of products for multimedia applications grow, the need for testing methods and fidelity metrics becomes critical. Testing devices are important for the development and evaluation of multimedia products, for example, to assess MPEG coding fidelity.
It is important to test digital coders/decoders during either their development or installation. However, assessing picture quality in the digital domain is a problem because it involves human perception. The most commonly used metric, the signal-to-noise ratio, does not match human judgment well. See, for example, P. M. Farrelle, Recursive Block Coding for Image Data Compression, Springer Verlag, New York, 1990.
Furthermore, conventional digital transmission testing systems typically transmit and evaluate natural scenes. This approach has several disadvantages. Natural scenes are resolution dependent and hence are difficult to produce with varying frame rate or size. Furthermore, complex natural scenes can require a large amount of memory to store and provide little latitude in testing the features of a particular coder due to the inflexibility of these scenes. Moreover, the test patterns are not deterministic (that is, we do not know the equations producing them), which makes quality evaluation difficult.
Thus, it can be seen that conventional digital testing systems using natural scene testing techniques impose limits upon current digital video testing devices, and hinder the use of these devices in many applications.
Therefore, there is an unresolved need for an automatic testing device that can test a video sequence coder/decoder system to assess the quality of decoded sequences and rate the fidelity of the coding chain in a way that correlates well with human assessments.